The present invention relates to actuators for valves and similar devices and, more specifically, to an adjustable linkage that will assure accurate operation of the valve through many cycles.
In a large number of industrial sites, valves, often in remote locations, require actuation by electrical or hydraulic devices. It is desirable, of course, that such devices operate reliably through many cycles to reduce the cost of attending to these devices and their associated valves. To achieve this, the actuator device must be properly installed and positioned relative to the valve elements it is intended to operate. In some types of environments, valves are employed that require substantially precise manipulation in order to effectively control fluids in their associated conduits. This is particularly true in fluid metering operations.
For many types of valves, the actuation device will only require infrequent operation so that the valve will stand idle for long periods. In other situations, the fluid being handled by the conduit may be of the consistency that renders operation of the valve difficult. In either case, a valve actuator is likely to encounter elevated torque initiation of a valve opening or closing operation. In such circumstances, it is important that the installation of the valve actuation device be accurate and in proper alignment to assure the maximum mechanical advantage upon actuation.
In the past, valve actuators required time consuming installation to assure accurate operation. Adjustment of the actuators was often difficult to achieve so as to assure such accurate operation over many opening and closing cycles.
The present invention provides a valve actuator that provides a solution to a number of the design and operational difficulties encountered in prior art actuators. Specifically, the present invention provides an adjustable linkage for transmitting motion from a power source which may be either hydraulic, mechanical or electrical to a valve stem to accurately effect rotation of the valve stem while minimizing stress to the linkage itself. In one embodiment, a rectilinear track or tracks are provided in housing walls with the tracks extending parallel to each other. Slider members are positioned in each track for reciprocating movement and are moved in their respective tracks by an external actuator such as an electric motor mounted externally of the housing or by a piston rod which will be hydraulically actuated. The slider members will carry a pivot pin to which one or more linkage arms are connected. The other end of the linkage arms are connected to a lever arm through another pivot pin and this latter lever arm is connected to the operating stem of a valve. The pivot pins"" cross-sections are eccentrically shaped over a portion of the length of a respective pin to allow precise adjustment of the orientation of the linkage arms relative to the slide groove and the connecting lever arm connected to the valve stem. This will assure proper adjustment of the linkage arm and lever arm to obtain the greatest possible mechanical advantage provided by these members. In such a condition, the maximum torque will be available to operate the stem and the stress imposed on the linkage and lever arms will be reduced.
The foregoing and other advantages will become apparent as consideration is given to the following detailed description taken in conjunction with the accompanying drawings, in which: